Thermostat switch

ABSTRACT

Thermostat switch with metallic, flexible, contact-point plates positioned longitudinally within a thermosensitive sleeve. The two flexible plates are coupled at one end thereof, through a support, to one end of the sleeve and at the opposite end thereof, through another support and a screw rod, to the other end of the sleeve. With a temperature change, the sleeve expands or contracts more than the flexible plates, thereby causing these plates to flex closer to, or away from, each other and thus make or break the thermo-contact. The first mentioned support support has a reduced diameter section which minimizes the delay in thermostatic response to temperature changes. Means for preventing the flexible plates from distorting and for keeping the sleeve moisture-tight are included.

United States Patent Kondo 1 June 27, 1972 THERMOSTAT SWITCH Primary Examiner-Harold Broome Assistant lxaminerDewitt M. Morgan [72] Inventor: Kenshi Kondo, No 3-5, Ohkura l-chome, Attorney C1arioceccon Setagaya-ku, Tokyo, Japan 22 Filed: Nov. 30, 1970 211 Appl. No.: 93,588 [57] ABSTRACT Thermostat switch with metallic, flexible, contact-point plates 52 us. (:1 ..337/392, 337 394,337 400 bngimdinany a hemmnsiive 51cm- The [51] "Hmh 37/20 01h 37/48 two flexible plates are coupled at one end thereof, through a 58 Field of Search ..337/384, 386, 392, 394, 397, MP0", end the Sleeve and PP end 337 B98, 399, 400 thereof, through another support and a screw rod, to the other end of the sleeve. With a temperature change, the sleeve ex- 5 References Ci pands or contracts more than the flexible plates, thereby causing these plates to flex closer to, or away from, each other and UNlTED STATES PATENTS thus make or break the thermo-contact. The first mentioned 2,307,867 1/1943 Smith .337/394 x suPPolrt has a reduced diameer Swim which 2,698,367 12 1954 P6111215", ..337 39s minimizes the delay in thermostatic P to temperature 2 257 990 10 1941 Turenne 337 392 changes. Means for preventing the flexible plates from distort- 2,619,567 1 1952 walbn'dgeu 3 7 x ing and for keeping the sleeve moisture-tight are included. 2,090,407 8/1937 Turenne ..337/399 FOREIGN PATENTS OR APPLICATIONS 228,389 11/1957 Australia ..337/392 PATENTEDJWY m2 SHEET 10F 2 FIG. 3

FIG. 2

FIG. 4

INTRODUCTION This invention relates to a thermostat switch and,.in particular, concerns'a thermostat switch in-whichthe differential expansion or contraction between two metals having difl'erent coefficients of thermal expansion is utilized to effect switching action.

THE PRIOR ART Thermostatic switches utilizing the differential expansion and contraction'between' two dissimilar'metals have long-been in common use. An example of such a switch has a'pair of contact-point carrying plates housed in a thermosensitive'tube or sleeve and such a differential movement causes the contactpoint carrying plates to be tensioned' or compressed'to make or break the contact between the two contact points carried by these plates. In thermostatic switches of this kind, the pair of contact-point carrying plates are required to retain their correct position at all times and be subjected to temperature changes concurrently with the thermo-sensitive sleeve without any time lag, otherwise the thermostatic switching action will not take place accurately and precisely at a desired or settemperature.

It is diflicult to satisfy the above requirements for the following reasons. For example, in such a thermostatic switch, a temperature setting is accomplished by rotating a screw rod which is engaged with a support, holding one end of the pair of contact-point carrying plates. These plates however, are twisted by the rotation, and their correct position is consequently gradually distorted. Moreover, both ends of the plates are necessarily connected to both ends of the thermosensitive sleeve by connecting means,-these means must be mechanically strong in order to hold the pair of said plates in correct position. However, if these means are of large mass in order to obtain greater mechanical strength, they will have a large thermal capacity and hence may prevent the pair of said plates from becoming subjected to temperature changes concurrently with the thermo-sensitive sleeve. In other words, the temperature of the contact-point carrying plates might start changing less quickly than that of the sleeve upon occurrence of a temperature change in the environment.

BRIEF SUMMARY OF THE INVENTION An object of this invention is to provide a thermostat switch that opens and closes accurately and precisely at the desired or set temperature by overcoming the aforesaid drawbacks.

In conventional switches of this kind, electrical lead wires are connected to the contact points on the plates, and are extended through the sleeve to outside thereof for connection with a external circuit. The outwardly extending portions of the wires are not free from the chances of being jerked or pulled. Such a pull would act on the contactpoints, thereby distorting the position of the plates and obstructing the proper switching action. In addition, it is noted that the possibility-of the thermo-sensitive sleeve drawing moisture into its interior is large because, under normal service conditions, the ambient temperature alternates cyclically between a high level and a normal low level, causing the air within the sleeve to expand and contract alternately and hence making the sleeve breathe or inhale and exhale air.

Another object of theinvention is, therefore, to provide an thermostat switch, so improved that a tension exerted on the outside portions of the lead wires will not distort the contact point carrying plates inside the thermo-sensitive sleeve.

Still another object is to provide a thermostat switch in which the thermo-sensitive sleeve is perfectly sealed against moisture so as to inhibit the moisture to enter into the sleeve interior.

According to the invention, one end of the pair of contact point carrying plates is fixed to the one end of the thermo-sensitive sleeve through a support holding the plate, which support comprises three integrally constructed sections, namely,

Because of the smaller mass so introduced, the delay in thermostatic response of the switch to temperature changes is minimized.

Furthermore, according to the invention, the lead wires inside the sleeve are'coiled around the screw rod, so that a pull on the outside portion thereof will be abmrbed or cushioned off by the coiled portions and thus the contact carrying plates are protected against distortion due to such a pull.

Moreover, according to the invention, the thermo-sensitive sleeve is positively sealed by means of sealing members such as 0" rings provided between a grip and the sleeve and between the grip and an adjusting screw, in order to prevent the-permeation of moisture into the sleeve interior.

Furthennore, the outwardly extending portions of lead wires are of a poured sealing medium such as epoxy resin between the insulating sheaths and the conductors at their ends, so that the moisture penneating from the ends through the tubular insulating sheath into the thermo-sensitive sleeve is perfectly blocked.

THE DRAWINGS Additional objects and advantages of the invention will be apparent from the following descriptions regarding the specific embodiments of the invention when read in connection with the accompanying drawings, in which:

FIG. 1 is a cross sectional view illustrating the construction of the thermostat switch according to the invention;

FIG. 2 is a cross sectional view taken on the line A A of FIG. 1.

FIG. 3 is a perspective view of one of the plates supports.

FIGS. 4 and 5 are cross sectional views, respectively, illustrating other formes of thermostat switch according to the invention.

FIG. 6 is a perspective view of a lead wire terminal portion, illustrating a sealing structure adopted to the lead wire.

FIG. 7 is a diagrammatical view illustrating another form of contact point carrying plates and their supports.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG.- I, a pair of contact point carrying plates 8 and 8' whose ends are held by supports 2 and 6, are contained in thermo-sensitive sleeve 1. The support 2 consists of a bottom plate section 3 welded to and closing one end face of the sleeve 1, a contact point carrying plates mounting section 5 which is short in length and has substantially cylindrical shape, and a reduced diameter section 4 which interconnects the sections 3 and 5. Said sections 3, 4 and 5 are integral, as shown in FIG. 3, and are formed by machining a single block. The peripheral portion of the mounting section 5 has two opposite flats 51 and 52 parallel to each other. To these flats, the ends of the plates 8 and 8 are spot-welded. The thickness T of bottom plate section 3 is made substantially equal to that of the wall of sleeve 1 in order to give to this plate section the same thermal characteristic as that of the sleeve 1. The reduced diameter section 4 is sized so as to possess a mechanical strength large enough to hold the plates 8 and 8. An inordinate thickness of the section 4 will increase the delay in thermostatic response to temperature changes and is therefore undesirable.

The other support 6 comprises a contact point carrying plate mounting section 7, which is shaped identical to said mounting section 5 except for a through hole 12 provided along its center line. The other ends of the plates 8 and 8' are secured to the parallel flats formed on the peripheral portion of the mounting section 7. A screw rod 13, whose inner end 14 carries a guide plate 15, extends through said hole 12 with an ample radial clearance. Said plate 15, as shown in FIG. 2, is shaped to conform at its two edges to the inner surface of sleeve 1. Notches l6 and 16', provided in the two conforming edges of plate 15, fit the corresponding guide ribs 17 and 17 formed on the diametrically opposed portions of the wall of sleeve 1 where the mounting section 7 is located. The outer end of the screw rod 13 is provided with screw threads 13', which engage the inner surface of a hole 21 provided in an adjusting screw 19. Screw threads 22 are cut on the outer surface of the adjusting screw 19. The threads 22 of the adjusting screw 19 cooperate with screw threads in the central hole 23 of the plug 18 secured to the sleeve 1 at its other end portion. The head portion of the adjusting screw 19 is provided with a slot 19 for admitting the tip of a screwdriver. Fitting the screwdriver tip into this slot 19' and turning it will rotate the adjusting screw 19, causing the rod 13 and the guide plate 15 to be advanced or retracted in axial direction, depending on the direction of screwdriver rotation, with the guide plate 15 sliding on the guide ribs 17 and 17' thereby altering the axial clearance d between the mounting section 7 and the guide plate 15.

The plates 8 and 8' are bent respectively toward each other so as to fonn a flattened V" shape. Insulators 9 and 9', made of for example mica, are wrapped around the middle portions of the plates, and metal plates 10 and 10', each carrying a contact point 11 or 11, are mounted on said insulators 9 and 9' by, for example, embracing the insulator, so that the contact points 11 and 11' are mounted on the plates 8 and 8'. To the metal plates are soldered the ends of lead wires 24 and 24', the lead wires being drawn out through the hole 20 of the plug 18 to the exterior of the sleeve 1.

The operation of the thermostat switch constructed as above described will not be explained by assuming first that the ambient temperature rises when contact point carrying plates 8 and 8' are in the relaxed state, keeping their contact points 11 and 11' in full contact. As the temperature rises, the sleeve 1 will expand lengthwise more than plates 8 and 8, so that the clearance d decreases progressively and eventually becomes zero. When the clearance becomes zero, the guide plate 15 abuts against the mounting section 7, and the sleeve 1 which expands as the temperature rises exerts a pull on the pair of the plate 8 and 8', thereby causing them to assume a more flattened V shape. Thus, the contact points 11 and 11' having been closed up to now will be opened. The foregoing sequence of operation will reverse when the temperature drops after the switch has opened.

According to the invention, the support 2 holds the assembly of the plates 8 and 8' and the other support 6 firmly in the sleeve 1 since the bottom plate section 3 is secured to the sleeve end by welding. In conventional thermostat switches, however, the ends of the plates corresponding to plates 8 and 8' were bent to a right angle; the angled portions were overlapped one upon the other and fastened together by means of an eyelet; a short rod having a large-diameter head was passed through the hole of the eyelet with some radial clearance; and a bottom end of the short rod was studded rigidly in a hole in a bottom plate section. A clearance corresponding to the clearance d mentioned above was introduced between said large diameter head and the end face of said eyelet. The screw rod did not have the present guide plate 15 but, instead, was secured rigidly to a support like support 6. In such a prior art switch construction, the pair of contact point carrying plates within thermo-sensitive sleeve are not fixedly settled but are liable to totter even though the bottom plate section is welded to the sleeve end. Such contact point carrying plates are likely to become distorted in the course of service and cause malfunction of the contact points. This drawback is completely eliminated in the present invention. Moreover, according to the invention, because of the reduced diameter of the section 4, the support 2 is enabled to possess a lesser amount of mass and hence a smaller thermal capacity than when the section 4 has the same diameter as that of the bottom plate section 3. Thus, in the switch according to the invention, the delay in temperature change is minimized owing to the small thermal capacity of the support 2.

FIG. 4 illustrates another embodiment of the invention, in which parts similar to those of FIG. 1 are identified by similar numerals. In this embodiment, the plug 18 is located at some distance inwardly from the end of the sleeve 1 and secured there to the sleeve, whose end is fitted with and closed by a lid 25, thereby introducing an enclosed space 28 in the sleeve between the plug 18 and the lid 25. A through hole 27, not threaded, is provided centrally in the lid 25 to pass the adjusting screw 19 outwardly. That portion of adjusting screw 19 in the space 28 is surrounded by several turns of the lead wires 24 and 24', which then emerge from the space 28 through the hole 26 in the lid 25. By this construction, any tension applied to the emerging portion of the lead wire will not influence the plates 8, 8' because such a tension will be absorbed or taken by the turns of lead wires in space 28. In still another embodiment shown in FIG. 5, a grip 30 is provided over the plug 18. The gn'p 30 has, in the interior portion thereof, a bore 32 having a smaller diameter and a bore 33 having a larger diameter, both bores being interconnected by a step 31. The bore 33 is threaded and the plug 18 is screwed into the bore, with an 0" ring 34 interposed between the step 31 and the end face of plug 18 to seal the gap between the members 18 and 30. The adjusting screw 19 passes through the hole 32 and extends out of the grip. On the end face of the grip 30 is provided a depression 35, to which an 0" ring 36 is seated to seal a gap between the grip and the adjusting screw. The outer end part of screw 19 carries a knob 39; and a dial disc 37 is fastened by securing screws 38 to the end face of grip'30 and retains O ring 36 in compressed state to ensure the positive sealing action of this ring. A cap 40 is threadedly fitted over the grip 30, both being preferably made of plastic material and shaped by molding.

A small hole 41 is bored from the periphery of the grip 30 to the small bore 32. The lead wires 24 and 24' extend out through this hole 41 from the small bore 32. Into the hole 41 in the vicinity of the periphery of the grip a packing 42 is inserted and compressed by nut 43 to seal the clearance around the lead wires in hole 41. A sealing compound of such as epoxy resin is poured into a hole 44 in the nut 43 to complete the seal.

Permeation of moisture into the thermo-sensitive sleeve 1 is substantially blocked by the 0" rings 34 and 36 and the packing 42, but this inventor has experimentally discovered that moisture could find its way through the clearance, between the conductor and the insulating sheath of the lead wire. According to the invention, therefore, a sealing compound is injected into each lead wire, that is, between the conductor and the insulating sheath at the end of the lead wire. How this is accomplished is illustrated in FIG. 6, wherein a terminal 45 having a tubular portion, not shown, is connected with the conductor and an insulating tube 46 is covered onto the sheath halfway to leave its portion 47 over the connection of conductor with the terminal 45. The portion 47 is fastened to the said tubular part of the terminal 45 by pinching. Using such a tool as a syringe, the sealing compound 26 is injected into the lead wire so that the compound will penetrate over some distance, for example to a depth marked by a dotted line 48, thereby making the sleeve 1 completely tight against moisture.

FIG. 7 illustrates a further modified embodiment designed to close the contact points when temperature rises to a set level, and shows its contact point arrangement for accomplishing this switching action. It will be seen that the mounting sections 5 and 7 are, in this case, provided with slots 54, 74 at the center. The ends of contact point carrying plates 8 and 8 are inserted into the slot 74 on the one end, and into the slot 54, on the other end, and are secured rigidly to these mounting section by such means as welding. Under normal conditions of service, the contact points 11 and 11' and the plates 8 and 8' are in the state shown in FIG. 7, With a rise in ambient temperature, the plates 8 and 8' become tensioned on account of ments of the invention, it will be obvious to those skilled in the art that the thermostat switch described herein is capable of various modifications, and is to be taken as illustrative rather than limiting within the spirit and scope of the invention.

the resultant differential expansion previously explained, to bring the contact points 1 l and 11' into contact, thereby making the circuit through the switch.

Having set forth and described with the particular embodi- What is claimed is l. A thermostat switch comprising:

a. a thermo-sensitive sleeve adapted to contract and expand in response to changes in ambient temperature;

b. a pair of contact point carrying plates each including a contact point proximate the middle section thereof;

bottom section secured to and closing one end of said sleeve, said bottom section having a thickness substantially the same as the wall thickness of said sleeve, a mounting section to which one end of said carrying plates is secured and a section of reduced diameter intermediate and integrally interconecting said bottom section and said mounting section of said first support;

. a second support for said plates, said second support including a hole therethrough and a mounting section to which the other end of said carrying plates is secured;

. a threaded screw rod extending through said hole in said second support;

. a guide plate carried by the inner end of said screw rod and including anti-rotation means cooperating with the inner surface of said sleeve;

. a tubular adjusting screw having first threads formed on its outer surface and second threads formed on its inner surface, said second threads being in mating engagement with said threaded screw rod;

h. a plug secured to said sleeve proximate the end thereof opposite said first support, said plug having a threaded a first support for said plates, said first support including a 15 hole therein that is in mating engagement with said first threads of said adjusting screw, said plug further including threads on the external surface thereof;

. a grip including a first larger diameter, threaded bore, a second smaller diameter bore and a step portion interconnecting said first and second bores, said external threads of said plug being in mating engagement with said larger diameter threaded bore of said grip, said adjusting screw extending through said smaller diameter bore to the exterior of said grip;

j. a knob attached to the outer end of said adjusting screw for adjusting the temperature setting;

k. a first O-ring positioned about said adjusting screw;

1. a dial disc having a hole therethrough for receiving said adjusting screw, said dial disc being secured to said grip and arranged to compress said first O-ring for sealing a gap between said O-ring and said adjusting screw; and

m. a second O-ring positioned between said step portion in said grip and said plug for sealing a gap therebetween 2. A thermostat switch according to claim 1, in which a small hole is bored from the periphery of said grip to said small small-diameter bore, and there are further included insulated lead wires, whose inner ends are connected with said pair of contact points, being passed through said plug into said smalldiameter bore, wherein said lead wires are coild around said adjusting screw for several turns, and then drawing out through said small hole; and a sealing means embedding a gap between said insulated lead wires and said grip is provided in said small hole at a vicinity of the periphery of said grip.

3. A thermostat switch according to claim 2, in which the ends of said lead wires emerging from said grip are connected with a terminal respectively, a sealing compound being injected from the end of each lead wire into the clearance between the conductor and the insulating sheath thereof. 

1. A thermostat switch comprising: a. a thermo-sensitive sleeve adapted to contract and expand in response to changes in ambient temperature; b. a pair of contact point carrying plates each including a contact point proximate the middle section thereof; c. a first support for said plates, said first support including a bottom section secured to and closing one end of said sleeve, said bottom section having a thickness substantially the same as the wall thickness of said sleeve, a mounting section to which one end of said carrying plates is secured and a section of reduced diameter intermediate and integrally interconecting said bottom section and said mounting section of said first support; d. a second support for said plates, said second support including a hole therethrough and a mounting section to which the other end of said carrying plates is secured; e. a threaded screw rod extending through said hole in said second support; f. a guide plate carried by the inner end of said screw rod and including anti-rotation means cooperating with the inner surface of said sleeve; g. a tubular adjusting screw having first threads formed on its outer surface and second threads formed on its inner surface, said second threads being in mating engagement with said threaded screw rod; h. a plug secured to said sleeve proxImate the end thereof opposite said first support, said plug having a threaded hole therein that is in mating engagement with said first threads of said adjusting screw, said plug further including threads on the external surface thereof; i. a grip including a first larger diameter, threaded bore, a second smaller diameter bore and a step portion interconnecting said first and second bores, said external threads of said plug being in mating engagement with said larger diameter threaded bore of said grip, said adjusting screw extending through said smaller diameter bore to the exterior of said grip; j. a knob attached to the outer end of said adjusting screw for adjusting the temperature setting; k. a first O-ring positioned about said adjusting screw; l. a dial disc having a hole therethrough for receiving said adjusting screw, said dial disc being secured to said grip and arranged to compress said first O-ring for sealing a gap between said O-ring and said adjusting screw; and m. a second O-ring positioned between said step portion in said grip and said plug for sealing a gap therebetween
 2. A thermostat switch according to claim 1, in which a small hole is bored from the periphery of said grip to said small small-diameter bore, and there are further included insulated lead wires, whose inner ends are connected with said pair of contact points, being passed through said plug into said small-diameter bore, wherein said lead wires are coild around said adjusting screw for several turns, and then drawing out through said small hole; and a sealing means embedding a gap between said insulated lead wires and said grip is provided in said small hole at a vicinity of the periphery of said grip.
 3. A thermostat switch according to claim 2, in which the ends of said lead wires emerging from said grip are connected with a terminal respectively, a sealing compound being injected from the end of each lead wire into the clearance between the conductor and the insulating sheath thereof. 